receiver

#include "net.h"
int main (void)
{
    int fd = -1;
    struct sockaddr_in sin;
    /* 1. 创建socket fd */
    if ((fd = socket (AF_INET, SOCK_DGRAM, 0)) < 0) {    //udp程序
        perror ("socket");
        exit (1);
    }
    /* 2. 允许绑定地址快速重用 */
    int b_reuse = 1;
    setsockopt (fd, SOL_SOCKET, SO_REUSEADDR, &b_reuse, sizeof (int));
    /*加入多播组*/
    struct ip_mreq mreq;
    bzero(&mreq, sizeof(mreq));
    mreq.imr_multiaddr.s_addr = inet_addr(MULTICAST_IP);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP,&mreq, sizeof(mreq));
    /*2. 绑定 */
    /*2.1 填充struct sockaddr_in结构体变量 */
    bzero (&sin, sizeof (sin));
    sin.sin_family = AF_INET;
    sin.sin_port = htons (SERV_PORT);    //网络字节序的端口号
    /* 让服务器程序能绑定在任意的IP上 */
#if 1
    sin.sin_addr.s_addr = htonl (INADDR_ANY);
#else
    if (inet_pton (AF_INET, SERV_IP_ADDR, (void *) &sin.sin_addr) != 1) {
        perror ("inet_pton");
        exit (1);
    }
#endif
    /*2.2 绑定 */
    if (bind (fd, (struct sockaddr *) &sin, sizeof (sin)) < 0) {
        perror ("bind");
        exit (1);
    }
    char buf[BUFSIZ];
    struct sockaddr_in cin;
    socklen_t addrlen = sizeof (cin);
    printf ("\nmulticast demo started!\n");
    while (1) {
        bzero (buf, BUFSIZ);
        if (recvfrom (fd, buf, BUFSIZ - 1, 0, (struct sockaddr *) &cin, &addrlen) < 0) {
            perror ("recvfrom");
            continue;
        }
        char ipv4_addr[16];
        if (!inet_ntop (AF_INET, (void *) &cin.sin_addr, ipv4_addr, sizeof (cin))) {
            perror ("inet_ntop");
            exit (1);
        }
        printf ("Recived from(%s:%d), data:%s", ipv4_addr, ntohs (cin.sin_port), buf);
        if (!strncasecmp (buf, QUIT_STR, strlen (QUIT_STR))) {    //用户输入了quit字符
            printf ("Client(%s:%d) is exiting!\n", ipv4_addr, ntohs (cin.sin_port));
        }
    }
    close (fd);
    return 0;
}